Lead scientist Dr Jian-Ping Cai, from the National Centre of Gerontology in Beijing, China, said: “Oxygen by-products produced during normal metabolism can cause oxidative damage to biomolecules in cells, such as DNA and RNA.

“As we age, we suffer increasing oxidative damage, and so the levels of oxidative markers increase in our body.”

After encouraging results from animal studies, the team measured levels of 8-oxoGsn in urine samples from 1,228 Chinese residents aged between two and 90.

“We found an age-dependent increase in urinary 8-oxoGsn in participants 21 years old and older,” said Dr Cai. “Therefore, urinary 8-oxoGsn is promising as a new marker of ageing.

“Urinary 8-oxoGsn may reflect the real condition of our bodies better than our chronological age, and may help us to predict the risk of age-related diseases.”

While levels of the molecule were roughly the same in men and women, they were higher in post-menopausal women, possibly for hormonal reasons, said the researchers.

The results, published in the journal Frontiers in Aging Neuroscience, were questioned by British expert Professor Ilaria Bellantuono, from the University of Sheffield.

She said: “Ageing is not a disease but a risk factor for age-related diseases, in the same way smoking is for lung cancer. Therefore it is not possible to say whether this could be used as marker to predict the occurrence of disease.”